Predicting periodic evolution of BUE formation mechanisms during machining ductile material using damage mechanics

Abstract

Built-up edge (BUE) formation in machining maintains a profound effect on the cutting operation, such as cutting forces, cutting temperatures, tool wear, tool life, cutting vibration, surface roughness and the geometric dimensions of machined products and so on. Recently, attempts have been made to use BUE as the tool cutting edge/wedge to optimize machining, extend the tool life, etc. In order to have a clearly understanding of BUE formation, cutting experiments were performed on aluminum alloy A6063-T5 and low carbon steel STKM11A using the cemented carbide tool over a wide range of cutting speeds. The cutting speed of BUE formation spans just a small range of the cutting speed under low cutting speed and disappears with increasing the cutting speed, which is found to be ascribed to the decrease of cutting force and thermal effects that caused by increasing cutting speed. Further microscopic observations reveal that the temperature, plastic shear and shear rate in secondary shear zone are significantly related to BUE formation, which increases with increasing the cutting speed. Since the chip thickness ratio is an important parameter to characterize the chip plastic deformation, the relationship between the chip thickness ratio and BUE formation is considered. In this work, a new theoretical damage model is developed to predict the evolution of BUE formation, in which the reduction of material properties due to the thermal effects had been considered. And the model validation is performed by comparing the experimental results with the simulations for aluminum alloy A6063-T6 and low carbon steel STKM-11A, which clearly shows that the proposed analytical BUE formation model is able to predict the periodic evolution of BUE formation. Not only the cycle time can be predicted, but also it makes a more clearly understanding of the evolution of BUE formation mechanism and its effects.